Ultrafast dynamics of electrons excited by femtosecond laser pulses: Spin polarization and spin-polarized currents
Ultrafast dynamics of electrons excited by femtosecond laser pulses: Spin polarization and spin-polarized currents
复制标题
飞秒激光脉冲激发的电子超快动力学：自旋极化和自旋极化电流
作者：
O. Busch;Franziska Ziolkowski;I. Mertig;J. Henk
入射到铁磁样品上的激光辐射会产生受激发的电子和电流，其自旋极化不得与磁化强度对齐--这是由于自旋轨道耦合在自旋和角度分辨光电子发射中普遍存在的一种影响。本文系统地研究了飞秒激光脉冲产生的自旋极化和自旋极化电流的动力学，在我们的理论框架内进行了模拟。自旋极化强烈地依赖于激光脉冲的性质和样品的组成，这一点通过对Cu(100)、Co(100)和Co/Cu异质结的比较结果表明。我们发现了一个从激光脉冲最大值之前的相干性到之后的非相干性的转变。此外，由自旋-轨道耦合引起的自旋极化分量的时间依赖关系在铜和钴中有很大不同：在铜中，我们发现有微小的快速调制的长周期振荡，而在钴中，显著的快速振荡与长周期的振荡是重叠的。信号在空间上的显著相关性突出了不均匀性的重要性，特别是磁/非磁界面作为超快自旋极化效应的源。我们的研究提供了飞秒激光激发期间和之后不久的电子动力学的详细见解。
Laser radiation incident on a ferromagnetic sample produces excited electrons and currents whose spin polarization must not be aligned with the magnetization -- an effect due to spin-orbit coupling that is ubiquitous in spin- and angle-resolved photoemission. In this Paper, we report on a systematic investigation of the dynamics of spin polarization and spin-polarized currents produced by femtosecond laser pulses, modeled within our theoretical framework EVOLVE. The spin polarization depends strongly on the properties of the laser pulse and on the sample composition, as is shown by comparing results for Cu(100), Co(100), and a Co/Cu heterostructure. We find a transition from coherence before the laser pulse's maximum to incoherence thereafter. Moreover, the time dependence of the spin-polarization components induced by spin-orbit coupling differ significantly in Cu and Co: in Cu, we find long-period oscillations with tiny rapid modulations, whereas in Co prominent rapid oscillations with long period ones are superimposed. The pronounced spatial dependencies of the signals underline the importance of inhomogeneities, in particular magnetic/non-magnetic interfaces `act as source' for ultrafast spin-polarization effects. Our investigation provides detailed insight into electron dynamics during and shortly after a femtosecond laser excitation.
影响因子：
38.3
作者：
Kampfrath, T.;Battiato, M.;Muenzenberg, M.
通讯作者：
Muenzenberg, M.